1. Field of the Invention
The present invention relates to an information storing disk for storing a system stream, and apparatus and a method for reproducing the system stream from the information storing disk. In particular, the present invention relates to an information storing disk for allowing a plurality of reproduction apparatuses having different levels of performance, such as data processing speed, to have the same wait time before the reproduction of the system stream starts, and an apparatus and a method for reproducing the system stream from the information starting time.
2. Description of the Related Art
Conventionally known optical disks for storing audio information and moving picture information to be reproduced therefrom include compact disks (CDs) and lesser disks (LDs).
A CD is an optical disk having a diameter of 12 cm and stores digital data obtained by encoding music information using an encoding technology referred to as linear PCM. CDs have been utilized as a medium for storing digital data for music applications.
An LD is an optical disk having a diameter of 30 cm and stores moving picture information, along with audio information, in the form of analog signals. LDs have been utilized as a medium for storing analog data for video applications such as movies.
Recently, new types of optical disks have been introduced. One of such new types of optical disks is an optical disk having a diameter of about 12 cm which realizes long-time recording/storing and a sufficiently high quality by efficient compression of music information and/or moving picture information including audio information. Another type of optical disk has a file structure with which data transmission with computers and communication devices is performed relatively easily.
Under such circumstances, an information storing medium which realizes storing and reproduction of audio data with a higher quality than compact disks have been demanded. As such an information storing medium, an optical disk in conformity with the DVD-Video format have been developed and implemented. Such an optical disk realizes storing and reproduction of audio data of a high quality of linear PCM, 96 kHz 24-bit sampling. However, with the DVD-Video format, it is impossible to reproduce high quality linear PCM multi-surround audio information or higher quality audio information.
High quality audio data contains a large amount of data and thus requires a high data transfer speed of audio data.
The present inventors have found, through many years of research and development on optical disks for storing high quality audio data, that the wait time before the start of reproduction of high quality audio data causes various problems.
Before the start of reproduction of information stored on an optical disk, the wait time is required, which is the time period from when one system stream to be reproduced among one or more system streams stored on the optical disk is determined until the reproduction of the one system is started. The wait time is also referred to as the "start-up period". A plurality of reproduction apparatuses having different levels of performance, such as data processing speed, usually have different start-up periods.
In the case of, for example, high quality audio data having a stream structure of the MPEG format, the start-up period includes time period T.sub.s, time period T.sub.c, and time period T.sub.m. Time period T.sub.s is a period required for the reproduction apparatus to seek to the position, on the optical disk, storing the audio data. Time period T.sub.c is a period from when the audio data is input to a decoder until the first correct decoded audio data is output from the decoder. Time period T.sub.c includes a period for adjusting output timing of a system stream with reference to a PTS (Presentation Time Stamp) including in the system stream and a period for examining whether or not the audio data included in the system stream is correct. Time period T.sub.m is a period for transition of a muting circuit is an analog output section from a mute state to a non-mute state.
In the case where a system decoder and an audio decoder are accommodated in separate chassis or mounted on separate LSIs, the start-up period is further extended because adjustment of the output timing based on the PTS and the examination on whether or not the audio data is correct need to be performed separately.
When the start-up period is extended, malfunction that the output timing for the system stream is not properly adjusted may undesirably occur in a specific reproduction apparatus and thus the leading audio data in the system stream is not reproduced.
When a plurality of reproduction apparatuses have different start-up periods, the inter-tune interval of an optical disk varies in accordance with the reproduction apparatus used. In such case, disk creators cannot uniformly set the inter-tune interval, which is significantly disadvantageous to the disk creators and users.